Linear fluid restrictor having a variable coefficient of restriction and method for making the same

ABSTRACT

A fluid flow restrictor having a resilient compressible body containing one or more fluid conductive passages is disclosed. The passages are of sufficient length with respect to their cross-sectional areas to insure laminar fluid flow therein when the body is in either a compressed or uncompressed state. The coefficient of restriction of the restrictor can be varied over a range of values, without altering the linearity of the fluid volume flow-to-pressure drop relationship thereof, by placing the body in various stages of compression.

United States Patent [72] Inventors Herbert M. Eckerlin Raleigh, N.C.;

Lawrence W. Langley, Corning, N.Y. [2l] Appl. No. 778,220 [22] Filed Nov. 22, 1968 [45] Patented Jan. 19, 1971 [73] Assignee Corning Glass Works Corning, N.Y.

a corporation of New York [54] LINEAR FLUID RESTRICTOR HAVING A VARIABLE COEFFICIENT OF RESTRICTION AND METHOD FOR MAKING THE SAME 5 Claims, 5 Drawing Figs. [52] US. Cl 138/46 [51] Int. Cl FlSd 1/02 [50] Field of Search 138/46, 45, 44, 40

[5 6] References Cited UNITED STATES PATENTS 2,241,086 5/1941 Gould l38/45X 2,319,498 5/1943 Gerard l38/45X 3,017,903 l/l962 Steffens 138/45 3,465 ,790 9/ 1 969 Everhard 138/45 Primary Examiner-Fred C. Mattern, .l r. Assistant Examiner-F. D. Shoemaker Attorneys-Clarence R. Patty, Jr. and Walter S. Zebrowski ABSTRACT: A fluid flow restrictor having a resilient compressible body containing one or more fluid conductive passages is disclosed. The passages are of sufficient length with respect to their cross-sectional areas to insure laminar fluid flow therein when the body is'in either a compressed or uncompressed state. The coefficient of restriction of the restrictor can be varied over a range olf values, without alter- I ing the linearity of the fluid volume flow-to-pressure drop relationship thereof, by placing the body in various stages of compression.

PATENTEUJAHIQIBYI l0 r e r r I Q l r.\\ I jI/l/l/l/l/l/l/ll/l/J Ill INVENTORS. Herbert M. E ckerlin Lawrence W. Langley ATTORNEY 'l/l/l/ll/l/l/I/I/l/ Eva/Fla: I

LINEAR r'wrn nes inrcroii ilA vluo a VARIABLE cor-:rrrcreuror ESTRICTIONA'ND METHODFOK ma rucrns'sme q gregarious or T iiafiisvEuTioN v Fluid restrictorssor valves having" laminar flow characteristics',}a linear relationship between'volume flow and pressure drop, and a variable coefficientflof restriction are known employed. f .1}

economyof fabrication.

to the prion'art. Suchprior art restrictors are characterized by a hard,"nonflexible =body inwhich aplurality of laminar flow fluid passages having fixed dimensions'existtThe coefficient-of restriction is variedovera rangeof values'by rotating acontrol which successively opensand close's theends of thepassages, oneor rnore'at a time. In such a manner the-passages'ar'e'discretely or stepwise placed in or removed from a set of parallel fluid flow pathsfl Y a v s Accordingly, such a restrictor'isllimitedto possessing a series ofdiscrete values of restriction coefficient. It is not possible to my the coeff cient in a smooth: continuous manner throughout a given range. Further, sucha restrictor'is relatively expensive to fabricate due'to the number of structural parts required and theifact'thattcoiitrollablejmoving parts mustbe sum/[Attic oFriierNveNrioN difficulties. R s r It is a furtherobject ofjthe instan riventionto provide a linear restrictor fvalv'e having a variable coefficient of restriction'which isparticularlv oharacterizedby its ease an'd Briefly; in -accOrdanCe withthe instant inventiona linear A DESCRIPTION OF THE PREFERREDEMBQDIMENTS Referring to FIG. 1 there is'shown acyli ndrical body 10 of compressible resilient material such as rubber, silicone rubber, teflon, urethane, or the like. However; the body. 10

may be of any desired cross-sectional shape such as rectangular. Extending through the-body 10 is; at least one fluid channel or passage 12. At the ends of the body l0'are a pair of terminals 14 through which a fluid can be introduced into and removedfrom the passages 12 by means of a pair of port fixtures l6. Fluid is introduced into the terminal 14 and thereafter apportioned between the passages 12 if more than one passage .12 e tists in proportion to the resistances offered by each of the passages 12 to theentry of the fluidtherein.

The-fluid flows through the passages 12, mikes together and is accumulated infthe enclosed region [[8 within the terminal 14 after which it flows out ofthe terminal 14 through the port .16.

In order that the restrictor or valve of the instant example provides a linear relationship I between fluid volume flow therein and pressure dropthereacross, it is necessary that fluid "flow in the passages 12 be laminar. As isw'ell known to those (skilled inthe art,1 laminar flow'properties require that the "length of s the passages 12 should' be relatively long in comparison to the cross*sectional are'afof the passages 12 so that nozzlelike-end effects are minimized, The limitsof length to cross-sectional area of the passages 12"which will permit laminar'flow thereincannot be stated withexactness as the roughness of the passage defining surfaces ofthe body 10, the.

viscosity of the particular fluid medium in use, the temperature of the fluid medium Reynolds Number. and a host of other well known variables allcontribute tothe nature of laminar fluid flow. .Where a large volume-flow capability is desired in "circumstances where the cross-sectional area-of the restrictor.havingavariable coefficient 'of restriction is provided having a .bo'cly of resilient compressible material c'on-.

' passages l2 must be kept small, the number of passages l2can be increased as'n ecessary. ln someca'ses the desiredflow capacity with laminar flow characteristics can be obtained by providing only afsingle passage'IZ. Ordinarily, the range of tainii'lg-atleast' one fluidpassagetherethrough having laminar propertie Byplaeihgthe body of the-restrictor incompr'essiorroyer'iat thecoefl'ficient-of restriction of *the-restric't or can be'changed over a range of values without altering thelinear-relationship between volume flow andpressuredrop;

least apo'rtion'of theilen'gth of are passage;

The restrictor ofthe instant invention can be fabricated by forrnir l'g a of resilient compressibl m'aterial in a mold of the desired shiip e'thro'ugh' which an'e' r o're wi'res having a selected diameterarefhe ld under sufficient tension'to keep them from bending or crimping; After the materialhas'cured or solidifiedij the Qmoldf'isremoved *{and the "wires are 3 withdrawn.,i\ppropnate end'terminations' may thereafter be' formed on the body to perinit fluid access to the passages, 'Additionalfobjects, features and advantages of the instant f z s V 'invention will become apparent to-those skilled in the art from 1 the following detailed descriptionjand attached drawing on which, by way ofexarnple, only the "preferred embodiments of] 'theinstantinvention'areillustrated; f

ekier 'bizscmmou or rne DRAWINGS FIG. 1 showsa partiallycross-sectionedelevation view of a embodiment of the instant inyentioltl Referringto'FlGS. 2 and 3 the restrictorof FIG. 1 is shown volume flow and pressure drop; properties desired will dictate the number of passages 12 requiredunder the influence of compressive forces, indicated by arrows, applied uniformly to'the-body 10 over a portion of the length of the passages 12 by a clamp or band 20. The action of the band 20 in bearing upon the body 910 produces constriction of l the cross-sectional areas of. the passages 12 with respect to their uncompressed state; 'This'in turn increases the coefficient ofrestrictioniof'the valve over that of its uncompressed statel l'iowever, the linearity of fvolume flow to pressure drop in the passages 12 is not alte'redover'a wide range of compression forces applied by the band 20 to the' body 10. It

- should be noted that the body 10' mustv be constructed of a shown, can be applied in any well known manner such as byapplying the compression plates 24 of a vise 26 to opposing surfaces of a body 22 as shown. Where the body of the restric- FIG. Zshows a fragmentary eleyation' view-partially cross- V v -.manner in which constriction of the fluid passages therein can FIG. 3 shows a cross-sectioned end view of the restrictorof FIG. 2 with a' band clamp attachedito'the body as viewed along lines3-3 thereof. l. I 1 FIG. 4 shows, in an oblique view, an example of the applica- 1 rectangular cross section to"alter the coefficient of restriction thereof. y y

FIG. 5 shows, in an oblique view, a stage in the fabrication "oftherestrictorofFlGS,l,2and3. j r r r v tion 3 of compression forces tothe body of a restrictor'of tor of the instant invention is of cylindrical shape as in FIGS. 1 and 2; a well known band clamp 20 is one example of the be obtained;

Referring to FIG. 5, there is shown. the manner'in which the 'restrictor of FIGS. 1, 2 and 3 can befabricated. A cylindrically shaped plastic tube 28 is provided as; a molding form through whichis drawn one or more wires 30'which are thereafter held stationary under sufficient tension to prevent them from bending or crimping. The number of wires .30 used corresponds to the number of passages 12 desired to be formed in the body type which will produce a resilient compressible material once the molding process is completed. A typical example of such material is Flexane, a urethane composition sold by the Devion Corporation of Danver, Massachusetts. The advantage in using Flexane is that it is curable at room temperature. The tube 28 has an inside diameter equal to the desired diameter of the body 10. The material of the mold or tube 22 is not critical and may be any suitable material which, when either coated or uncoated, will release from the material of body after it cures or sets. Flexane material is injected into the interior of the plastic tube 28 and permitted to cure or harden at room temperature. After curing is complete, the tube 28 is removed and the wires 30 are withdrawn leaving a compressible resilient body 10 of cylindrically shaped material having the desired fluid conductive passages therethrough.

The body 10 can just as well be molded in any desired shape such as in the form of a rectangular parallelepiped by the foregoing method. Any other material having suitable compressibility and resiliency can be used for the body 10 such as silicone rubber, rubber, or the like. Further, any suitable wirelike members 30 such as nylon thread, rigid cylindrically shaped rods of any material that will release from the body material, or the like can be used to form the passages 12 so long as their diameters are selected to provide the passages having the desired diameters.

Although the instant invention has been described with respect to specific details of certain embodiments thereof, it is not intended that such details be limitations on the instant invention except insofar as set forth in the following claims.

We claim: l. A fluid restrictor having a variable coefficient of restriction comprising: i

a body of resilient compressible material containing at least one fluid passage therethrough, said passage having a lengthto cross-sectional-area relationship so as to permit laminar flow to be maintained therethrough; and

means for compressing said body substantially perpendicular to the longitudinal axis thereof along at least a portion of the length of said passage whereby a linear relationship between flow volume and pressure drop is maintained. 2. The restrictor according to claim 1 further comprising terminating means attached to said body for providing fluid access to said passage.

3. The restrictor according to claim 1 wherein said body is in the shape of the cylinder, said at least one passage extending through said body parallel to the longitudinal axis thereof. 4. The restrictor of claim 1 wherein said resilient compressible material is selected from the' group consisting of rubber, silicone rubber, teflon, and urethane.

5. A linear fluid restrictor having a variable coefficient of restriction comprising:

an elongated parallelepiped body of resilient compressible material containing at least one fluid passage extending therethrough parallel to the longitudinal axis thereof; and

means for compressing said body along at least a portion of the length of said passage. 

1. A fluid restrictor having a variable coefficient of restriction comprising: a body of resilient compressible material containing at least one fluid passage therethrough, said passage having a lengthto cross-sectional-area relationship so as to permit laminar flow to be maintained therethrough; and means for compressing said body substantially perpendicular to the longitudinal axis thereof along at least a portion of the length of said passage whereby a linear relationship between flow volume and pressure drop is maintained.
 2. The restrictor according to claim 1 further comprising terminating means attached to said body for providing fluid access to said passage.
 3. The restrictor according to claim 1 wherein said body is in the shape of the cylinder, said at least one passage extending through said body parallel to the longitudinal axis thereof.
 4. The restrictor of claim 1 wherein said resilient compressible material is selected from the group consisting of rubber, silicone rubber, teflon, and urethane.
 5. A lInear fluid restrictor having a variable coefficient of restriction comprising: an elongated parallelepiped body of resilient compressible material containing at least one fluid passage extending therethrough parallel to the longitudinal axis thereof; and means for compressing said body along at least a portion of the length of said passage. 